JPS5899635A - Controlling circuit for air conditioner - Google Patents

Abstract

PURPOSE:To relieve the user of anxiety , by a method wherein a motor compressor is stopped with a predetermined lag of time from the operation of an operating/stopping switch, and the rotating speed of the compressor at the time of stopping is lowered to a value approximate to the minimum rotating speed. CONSTITUTION:A refrigerant-compressing cycle is provided by sequentially conconnecting the motor compressor 1, a condenser 3, a decompressor 4 and an evaporator 5; and an inverter controlling part 14 for controlling the frequency and voltage of a power source for the compressor 1 is provided. In a controlling circuit for the air conditioner, the compressor 1 is stopped with the predetermined lag of time from the operation of the operating/stopping switch 16, and the rotating speed of the compressor 1 at the time of stopping is lowered to a value approximate to the minimum rotating speed. Accordingly, the controlling part 14 will not be adversely affected by a counter electromotive force generated in the compressor 1 at the time of stopping, and the user can be relieved of the uneasiness due to the irregularity of the period of time required for stopping.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control circuit for an air conditioner having a refrigerant compression cycle, and particularly to a control circuit for a variable capacity air conditioner controlled by an inverter.

- In an air conditioner equipped with a refrigerant compression cycle in which an electric compressor, a condenser, a pressure reducer, and an evaporator are connected in sequence, and a blower is installed in the condenser and evaporator, the frequency and frequency of the power supply to the electric compressor are There is an inverter control method that controls the voltage, and this allows stepless control of the rotation speed, which is very effective in keeping room temperature fluctuations small. However, in this type of air conditioner, when the operation of the air conditioner is stopped, a back electromotive voltage may be generated in the compressor when electricity is turned off, which may adversely affect the inverter section. That is, the compression f when the current is turned off
i) The magnitude of the back electromotive force generated is determined by the energizing frequency,
That is, it is proportional to the rotational speed when turned off, and turning off suddenly at a high frequency will have a negative effect on the transistors in the inverter section, which is not very desirable.

Therefore, conventionally, as shown in the time chart of Fig. 4,
If a stop operation is performed at a point, the rotational speed of the compressor at that point is sequentially decreased at a fixed rate, and the compressor is stopped after reaching the minimum rotational speed. However, in this case, for example, when operating at maximum rotation speed, the point is 0 after T2 hours, and when operating at 65% rotation speed, T
They each stop at point B after one hour, and when operating at the minimum 30%, they stop at point A, so the time from pressing the stop switch to stopping the compressor varies depending on the operating condition at the time of stopping. This has the drawback of making the user feel uneasy.

In order to solve these problems, the present invention has been made with the object of providing a control circuit that can stop an electric compressor by delaying the operation stop operation by a certain period of time.

Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.
In the figure, 1 is a compressor, 2 is a compressor motor that drives this compressor 8!1, and these constitute an electric compressor. 3 is a condenser, 4 is a pressure reducer such as a capillary tube,
5 is an evaporator, which is connected to the compressor 1 in a closed circuit to form a refrigerant compression cycle. 6 is an outdoor blower provided corresponding to the condenser 3, and 7 is an indoor blower provided corresponding to the evaporator 5.

Reference numeral 8 denotes a general one-chip microcomputer (hereinafter referred to as "Maifun"), which has input terminals INI to IN3 and output terminals 0UTI to 0UT5, and also has a program ROM, data RAM, and ALU inside, and a reference clock oscillation section 9. It is driven by.

10 is a thermistor for detecting room temperature, and 11 is an A/D converter, which converts the room temperature detected by the thermistor 10 into a digital value and inputs it to the input terminal IN1 of the microcomputer 8. 12 is a variable resistor for setting the room temperature, and 13 is an A/D converter, which converts the room temperature set by the variable resistor 12 into a digital value and inputs it to the input terminal IN2 of the microcomputer 8. , 14 is an inverter section, in which AC power input from power terminals 15, 15' is rectified by diodes D1 to D, and smoothed by a capacitor C1o. Tr2' is V phase, transistor Tr3.
The three phases of the U phase are each controlled by the Tr 3' to generate a three-phase alternating current cycle, and the three-phase compressor motor 2 is operated. 16 is driving/
A stop switch is connected to the input terminal IN3 of the microcomputer 8. The microcomputer 8 reads the room temperature from the input terminal INI and the room temperature set value from the input terminal IN2, and controls the frequency and voltage of the three-phase voltages U, V, and W that supply electricity to the compressor motor 2 via the inverter section 14 based on these values. A signal is output from the output terminals 0UTI to 0UT3, thereby controlling the rotation speed of the compressor motor 2 and making the cooling capacity variable. The microcomputer 8 and the inverter section 14 constitute a so-called pulse width modulation type inverter control section. Note that the capacitors c,,c,'~ of the inverter section 14
Cs-C3' is a transistor Trl, Tri'-T
r3. This is to prevent Tr3' from malfunctioning due to noise. Also, resistor R3 and capacitor C,,R
4 and C,, R2 and C9, R5 and C,, R3 and C6, R,
and C9 are connected to transistors Tri and T by the back electromotive voltage after the compressor motor 2 is turned off.
ri'-Tr3. This is a discharge circuit for preventing damage to Tr3'. Control outputs for the outdoor blower 6 and the indoor blower 7 are generated at output terminals 0UT4 and 0UT5 of the microcomputer, respectively.

In the above configuration, the compressor 1 is driven by the compressor motor 2 during cooling operation. Then, the refrigerant compressed by the compression t is cooled and condensed by the air from the outdoor blower 6 in the condenser 3, then reduced in pressure by the pressure reducer 4, evaporated in the evaporator 5 to perform a cooling effect, and the indoor blower 7 Blows air to cool the room. Meanwhile, during this operation, the rotation speed of the compressor motor 2 is controlled via the microcomputer 8 and the inverter section 14 according to the room temperature, etc.
Variable cooling capacity. That is, if the room temperature rises, the microcomputer 8 determines this and increases the frequency and voltage of the three-phase voltage energized to the compressor motor 2 by the output from the inverter section 14. Therefore, the rotation speed of the compressor motor 2 increases, the cooling capacity increases, and the room temperature is lowered to the set temperature. On the other hand, if the room temperature drops too much, the rotation speed of the compressor motor 2 will decrease.

To stop the cooling operation, the operation/stop switch 16 may be turned off. For example, if the capacity variable width = frequency variable width is set to MAX loo Hz and MIN 30 Hz, the magnitude of the back electromotive force generated from the compressor motor 2 when the operation is stopped is approximately the same as the energizing frequency, that is, when off, as stated at the beginning. Therefore, a sudden re-off at too high a frequency will cause the transistors Tri, Trl'-Tr3 . Tr3
', which is not desirable. Therefore, the rotation speed of the compression rock motor 2 is lowered and then turned off. However, simply lowering the rotation speed causes variations in the stop time, which makes the user feel uneasy. make it work. In other words, as shown in the time chart of FIG. 2, the time from stop operation A of the run/stop switch 16 to complete stop E is kept constant, and the time opening is made to reduce the compressor motor 2 from the maximum rotation speed to the minimum rotation speed. For example, if you are driving at 65%, then 1
After reducing the rotation speed to the minimum rotation speed for 5 hours, the compressor motor 2 is operated at the same minimum rotation speed up to E, and then the compressor motor 2 is completely stopped. Also, if it is running at 30%, it will continue to run to E and then stop. That is, the AND condition of reaching the minimum rotation speed and reaching time T is taken, and thereby the compressor motor 2 is stopped. In this way, from the stop operation of the operation stop switch 16, the compressor motor 2
By lowering the rotation speed to the minimum rotation speed and making the time constant until it stops, it is possible to prevent the adverse effect of the back electromotive force on the inverter section 14, and at the same time, it is possible to eliminate the user's anxiety.

FIG. 3 shows another embodiment of the invention. This is to reduce the rotation speed of the compressor motor 2 at a rate of decrease corresponding to the rotation speed when the stop switch is operated, and to keep the time T until the rotation speed reaches the minimum rotation speed constant.

Note that the rotational speed of the compressor motor 2 when it is stopped does not necessarily have to be the minimum rotational speed, and can be sufficiently close to the minimum rotational speed. The outdoor blower 6 and the indoor blower 7 are the compressor motor 2
It may be stopped at the same time as the stop of , or it may be stopped before that.

As is clear from the above explanation, the present invention reduces the rotational speed of the electric compressor when it is stopped to a point close to the minimum rotational speed, so that the back electromotive force generated in the electric compressor when it is stopped is reduced. This does not have a negative effect on the inverter, and regardless of the rotational speed of the electric compressor when the stop switch is operated to stop, it is delayed by a certain delay time and then stopped, so the time to stop is reduced. It also eliminates the user's anxiety due to variations.

[Brief explanation of the drawing]

FIG. 1 is a control circuit diagram showing one embodiment of the present invention, FIGS. 2 and 3 are time charts showing its stopping operation, and FIG. 4 is a time chart showing a conventional example. 1: Compressor, 2: Compressor motor, 3: Condenser, 4: Pressure reducer, 5: Evaporator, 6: Outdoor blower, 7 Two indoor blowers, 8
: Microcomputer, 14: Inverter section, 162 Run/stop switch. Applicant Sharp Corporation Agent Tsunehisa Nakamura

Claims (1)

[Claims] In an air conditioner control circuit that includes a refrigerant compression cycle in which an electric compressor, a condenser, a pressure reducer, and an evaporator are sequentially connected, and an inverter control unit that controls the frequency and voltage of the power supply to the electric compressor, The electric compressor is stopped by a certain delay time after the operation of the stop switch, and the rotational speed of the electric compressor at the time of stopping is reduced to a point close to the minimum rotational speed. Air conditioner control circuit.